The leading cause of cognitive impairment in the U.S. elderly is Alzheimer’s disease. Because it is so common it is not unusual for both parents to develop the disease and presumably their offspring would be more likely to carry any genes associated with Alzheimer’s disease.

Suman Jayadev, MD, University of Washington, Seattle, and co-researchers, studied 111 families were both parents had developed Alzheimer’s disease. Of the 297 adult offspring:

23% developed Alzheimer’s disease,

31% of the offspring over 60 years showed signs of Alzheimer’s,

42% of the offspring over 70 years showed signs of Alzheimer’s.

Typically, the general population is expected to develop Alzheimer’s disease at the rate of approximately 6-13%. Of the 297 offspring in the study approximately 79% (189 offspring) had not reached 70 years, which suggest that the final incidence rate of 23% is underestimated and a rise of Alzheimer’s is expected in this group.

Having additional family members with Alzheimer’s disease did not increase the risk of developing the disease, but was associated with developing Alzheimer’s at an earlier age. Individuals with neither parent having Alzheimer’s the average onset of the disease was 72 years, when one parent had the disease the average age of onset for the disease was 60 years. If both parents had developed Alzheimer’s disease the average onset of the disease was at 57 years.

Researchers feel that families with significant occurrence of Alzheimer’s disease should be referred to Alzheimer’s disease research centers for further study.